1. Field of the Invention
The present invention relates to microwave divider and multiplier circuits in general and in particular to ultra low noise divider and multiplier circuits for use in dividing and multiplying microwave frequencies in ultra low noise microwave synthesizers and other microwave circuits.
2. Description of the Related Art
A microwave synthesizer is a circuit which is used for generating microwave signals of any frequency within a predetermined, generally broad, range of frequencies, e.g. 2 gigahertz (GHz) to 20 GHz.
Heretofore, noise performance pertaining to synthesized microwave signal generation, in particular sources that must produce any frequency, such as a synthesizer, has been limited by digital divider noise and the multiplying nature of harmonic samplers which heretofore has increased such noise by the harmonic number H of the sampler.
Digital divider noise has heretofore been a severely limiting factor in microwave circuits because of process dependent noise floors. For convenience, noise floors are defined herein in terms of noise power, in connection with which the units dBc/Hz are used. The units dBc/Hz represent the single sideband (SSB) noise power in a one (1) Hz bandwidth offset from the carrier by 10 KHz. For example, in T.sup.2 L circuits, which have a maximum operating frequency of approximately 100 megahertz (MHz), the noise floor is approximately -160 dBc/Hz. In MECL circuits, which have a maximum operating frequency of approximately 600 megahertz (MHz), the noise floor is approximately -150 dBc/Hz. In GaAs circuits, which have a maximum operating frequency of approximately 3000 MHz, i.e. 3 gigahertz (GHz), the noise floor is approximately -130 dBc/Hz.